Mine always have that banged up look =S Luckily, they grow new leaves rather easily. I remove all mechanically damaged leaves. Here's what mine looks like now: These below have teeth marks from one of my critters. I caught the cute pup jauntily walking across the room with one of these rosettes in her mouth =O I'm letting them sit for a few days before re-potting.

It’s normal to lose some of the lower leaves - they age out, or they get shaded out and the plant sheds them as they no longer do enough photosynthesis. Usually the rate of loss is less than the rate of replacement by new leaves but it sounds like you’re losing more than that. Maybe watering every three weeks is not enough, you may be stressing your plant too much. Of course it depends on the plant the soil the season the pot size etc etc, but my one dries down in 7-10 days and then I water it thoroughly and drain it well. Then wait again to dry down, as judged by the weight of the pot and/or whether a skewer inserted down to the bottom shows moisture. Read up on soils and watering on this forum, I think that’ll help. Don’t think it’s a disease. Could be rootbound though, looks a small pot for its size. Which will make it go through water faster too. I agree give it bright light.

CHEMICALS USED IN PULP & PAPER MANUFACTURING AND COATING Common NameChemical NameChemical FormulaUsed ForSpecific DensityOther CharacteristicsAgalite or TalcSilicate of MagnesiaMgO-32%, SiO2-62%It gives paper a greasy or soapy feel. and enables it to take a high finish.2.6 - 2.8A natural fibrous form of talc, gray in color.AKDAlkyl Ketene Dimer Sizing AlumSulfate of AluminaAl2(SO4)3.18H2OFor alkaline sizing along with Rosin1.62 AlbarineNatural Sulfate of LimeCaSO4.2H2O - 100%A calcium salt that is used for a variety of purposes including: building materials.2.4 Ammonium Zirconium Carbonate(AZC)Ammonium Zirconium CarbonateCH2O3NH3ZrUsed as in-solubilizer, crosslinker & hardener1.36AZC is a clear, usually colorless solution, having an odor of ammonia and a pH of approximately 9.5. As a carbonate, it will react with acids, and so should not be used in coating systems below pH 7. In storage, it is stable for up to six months.AnthraquinoneAnthraquinoneC14H8O2Added to white liquor (alkaline cooking liquor) to improve pulp yield and to increase the rate of delignification.1.44yellow crystalline powderAnti-Foam/Defoamer To prevent foam (anti-foam) or to destroy it once it has formed (defoamer). Surface active, but highly insoluble in water.AsbestineSilicate of MagnesiaMgO-32%, SiO2-62%It is used as a loading agent in paper manufacture, particularly for blotting papers and board.2.6 - 2.8A mineral compound of almost pure fibrous magnesium silicate, which possesses physical characteristics between those of talc and asbestos.APEAlkylphenol EthoxylatesCH3(CH2)n(C6H4) (OCH2CH2)m-OHUsed as cleaning agents or surfactants ASAAlkenyl Succinic Anhydride Sizing Barium SulfateBarium SulfateBaSO4 - 100%Used as a pigment4.2-4.5White insoluble powder.BarytesBarium SulfateBaSO4 - 100%Used as filler4.2-4.5 Blanc FixeBarium SulfateBaSO4 - 100%Used as a base for watercolor pigments and as a filler in paper.4.2-4.5Powdered barium sulfateCaseinA milk phosphoprotein Binder or adhesive in coating formulation CMCCarboxy Methyl Cellulose Sizing Caustic Lye or Caustic Soda or LyeSodium HydroxideNaOHPulping and to maintain pH Chalk (Precipitated)Precipitated Calcium CarbonateCaCO3 - 100%Filler particularly with acidic sizing coating pigment2.7-2.9High Brightness & OpacityChalk (French or Spanish)Silicate of Magnesia4MgO+5SiO2+H2O; MgO - 33%; SiO262% 2.6-2.9A soft white compact talcChina Clay, KaolinHydrated Silicate of AluminaAl2O3-40%; SiO2-46%; H2O-13%Filler, Coating2.4-2.7 Chlorine DioxideChlorine DioxideClO2In Pulp Bleaching2.86 Chlorine GasChlorineCl2In Pulp Bleaching and water treatment2.86 DolomiteCalcium Magnesium CarbonateCaMg(CO3)2Filler, Coating2.86 DTPADiethylene Triamine Penta Acetate Used for chelation (removal of transition metals from pulp). EDTAEthylene Diamine Tetra acetic Acid Used for chelation (removal of transition metals from pulp). Guar GumNatural Polymer Dry Strength Additive cationic derivativeGypsum or Mineral White or PlasterNatural Sulfate of LimeCaSO4.2H2OGypsum board,2.4 Hydrogen PeroxideHydrogen PeroxideH2O2In Pulp Bleaching3.13-3.4 LimeCalcium OxideCaOAlkaline Pulping Process Chemical Recovery, Bleaching3.13-3.4 Lime StoneCalcium CarbonateCaCO3To make Lime Precipitated CaCO3 is used as Filler and in Coating MagnesiteMagnesium CarbonateMgCO3 -100% 2.5 OxygenOxygenO2In Pulp Bleaching OzoneOzoneO3In Pulp Bleaching RosinAbietic AcidC19H29COOHSizing Rosin SoapSodium AbietateC19H29COONaSizing Salt CakeSodium SulfateNa2SO4. 10H2OMakeup chemical in sulfate pulping chemical recovery (Na2SO4. --- Na2S)2.4 Soda AshSodium CarbonateNa2CO3Makeup chemical in alkaline pulping chemical recovery (Na2CO3 +Ca(OH)2 ---2NaOH+CaCO3)2.43-2.51 Sodium DithioniteSodium HydrosulfiteNa2 O4 S2Bleaching2.20White crystalline powder with weak sulforous odorSodium SilicateSodium SilicateNa2SiO3In waste paper deinking for wetting, peptization, ink dispersion, peroxide stabilization. Starch.Comprised of glucose units linked together by oxygen bridges called glycosidesWet and dry end additive SulfurSulfurSTo make HSO3 for bi-sulfite pulping TitaniaTitanium DioxideTiO2Filler to increase the opacity and brightness of paper. Used in coating also.3.84-4.26

It's worth a try as long as you water it in correctly until it roots, and then feed it correctly once it's in (on Memorial Day...er, end of May as that's an American holiday!, the first of September, and around a month before ground freeze...hopefully October 1 for you folks). Use any good high-nitrogen fertilizer.