I agree with Keriann. Yes, you should really let them dry out. Matter of fact, once my seedlings are as big as yours, I let them dry out pretty much all the way before I water again. You can tell they need watered when you pick up the flat and it feels light as a feather. Then after you water, it's much heavier. Your method of bottom watering is quite unique, I must say. I think that most folks bottom water the way I do, which is to say setting the cells or cups into a tray of water and letting the plant absorb as much as it wants until you see moisture on the surface of the soil (usually takes anywhere from 5-20 min). Now, I can't say for sure what positive or negative effects your method of watering might have, except that it sure sounds like a pain in the hiney to me, and I somehow doubt that the soil is getting properly saturated. You want to simulate mother nature; a soaking rain. Then you want to let the soil dry out. That's how it is in nature. Roots need water yes, because the plant needs water, but then they need to dry out and get oxygen. Damp soil all the time = no oxygen to the roots. Now, I can't say for certain what part of your program is causing your issues, but I would start bottom watering them as described by letting them absorb water sitting in a tray. I think you will find that using this method, you should only have to water every 3-4 days, or less. I would lay off the ferts for a while, and then make sure only to fertilize when the soil is already damp, or you will burn the roots. I just mix the fert with water, then pour into a tray and bottom water as usual. Give this a shot, see if that doesn't help.

Orchid leaf

The brown spots appear to be common hydrangea leaf spots, sometimes a fungal infection called Cercospora Leaf Spot. See here for more info: http://www.aces.edu/pubs/docs/A/ANR-1212/ANR-1212.pdf Most of the time, this is caused by overhead watering. If you do this, try watering the soil instead and do it very early in the mornings. Clean up plant debris that may contain spores, discard leaves in the Fall on the trash and, if you can afford it and the problem is bad enough in your opinion, replace the mulch too. You can also apply fungicides and the article mentions some of them but they can be $$ expensive so I just follow those suggestions when it comes to the ones that I too have with leaf spot. I am not sure about the loss of leaves. Sounds mysterious since you have not mentioned anything that would account for that. Normally, this would require something like not watering it (the rootball dries out for example), winter damage or applying insecticides or fungicides to the plant or to nearby plants. Leaf spot can make the plant loose some of these leaves as they first appear to have the lesions and sometimes the leafs brown out and fall. But usually the infestation is not THAT bad. If Bluebird lost the leaves in this way then you may want to spray after all as that is kind of a big thing in my opinion. I normally see this issue on mine by late August or in September so this is kind of early. And I just live with the problem until the plant goes dormant in December. Then I carefully cut the leaves off without touching the stems (invisible 2016 Spring flower buds will usually be near the end of the stems).

Any damage that is showing on your plants is mechanical - that means it came to be from shipping and other transport, handling or jostling. It is not the result of diseases or insects nor does it look like any watering issues. In reality, these plants look pretty darn good considering most big box stores do not take the slightest bit of care with their plants (hence the evidence of damage you are seeing). As to fertilizing, you need to identify your plants and then do a bit of research, as not all plants benefit from similar fertilization methods nor do they require it at the same time. Cacti and succulents have different needs than do tropical foliage plants and flowering houseplants (orchids, African violets, flowering gift plants) have yet another set of needs. In general, an all purpose liquid fertilizer used at 1/2 to 1/3 strength with every other watering is appropriate for most tropicals during their primary growing season (March through October) but you can get by with quite a bit less. I'd suggest you post this on the House Plants forum both to get accurate ID's on your plants and their advice as to when, how much and with what to best fertilize what you have.