Just take some scissors and snip off the old/dead spikes. No need to sterilize. You're leaf tips are browning due to low humidity. Keep it bright, raise the humidity and if possible put it outside for late spring into fall. It will very high light and fall night-time temps down into the 40's to bloom again.

How deep is the mulch? And is water/rain getting through it to the roots? Perhaps dig up one plant to see what's going on underground. Oh yes, dahlias blacken if damaged by cold. Have you had colder than usual temps? As for the holes, finding out just what is chewing requires a bit of detective work. Look during the day, also at night, say about 10 pm or so. Be certain to investigate the undersides of the leaves as well as the tops.

These are very easy plants to care for, once you have a good understanding of their basic needs. They will even tolerate quite a bit of neglect. (Mine most certainly do, lol...) What they don't tolerate is the chlorine and/or fluoride that is in most tap water. As for using melted bagged ice, that will have no affect on the fluoride in the water. Neither boiling or freezing fluoridated water will do nothing to rid the water of fluoride. Which is why I just avoid using tap water on my spider plants altogether. Do that, and your spider plant will pretty much tolerate just about anything else. I've recently pruned off all of the offshoots from my Hawaiian spiders. So they can focus more on growing bigger, rather than branching out and growing so many little plantlets. Plus, the old branches were looking kind of ragged. It was long overdue for a "haircut" to help freshen them up a bit. Not to mention, the pots themselves were getting quite heavy. When I got finished, the pile of the little offshoots took up more space than the original mother plants, HaHa.

I would scrutinize my watering practices and see how the rose responds, Natasha. Watering twice a week is kind of insane for young roses trying to survive our dryness/heat during the summer, but I am sure you are aware that you must continue your diligence and figure it out. Adjusting your practices accordingly should reveal if the problem is watering, over-fertilizitation, or something like that. If the problem persists, I would remove the roses one by one, carefully potting them up in between waterings. Their new pot should prepared so once the rose is carefully removed, it can be placed directly in to the pot, covered with potting soil, a little compost, and watered without delay. It then should live in shade or open shade until it rebounds. Once showing health, it can be taken out into morning sun only for about 3-4 hours or so. Btw, you are correct, we are drier, with 4-4.5" of rain annually :(... just not quite as hot, nor for as long. You all get an extra month of that heat. We are beginning our extreme heat descent right now.