If you've been using the 1" tabs since forever already, you probably used too many and have to stop actually.
I suggest that you read Pool School (upper right of every page, white button) multiple times and particularly the information about tablets/pucks/tri-chlor and the residual CYA (cyanuric acid) they add to your pool. Most chlorine delivery and retention issues revolve around having too much CYA in the water. Pool school will help you understand how and why too much CYA is problematic.
Also, when you hear it recommended to have a proper test kit, know that it's really not optional and not a light recommendation. A good FAS-DPD test kit is actually essential. For now however, you can take your water to the pool store (directly, the sample can degrade over time) and get a full set of test results. They are often inaccurate, but it's ok to use as a guestimate right now.
Post back with these results, and we'll be better able to help you. Till then, we really don't know what's going on with your water and your guess is as good as ours as to what your solution really is.