Is three of them too much?

They will get too big for that tank, so they will have to be moved eventually.

8 a day is alot, even for three. I'd cut it back once every other or every 3rd day. And I agree with Chil (good advice as always). Get rid of the big common and let the two smaller ones establish some territories.

Do you feed them other things like zuchini or spinach or peas?

What are the measurments of your tank as that it is important for the plecos to have a lot of surface swimming area on the bottom of the tank.

I would have to say chil is right on this one. Also I would keep an eye on them. Even though commons arent very territorial but the gibbiceps is and will try to punk them around when it gets more size on him. 8 is alot for three man My single pleco (Finn) loves them my gibby stays on the wood but will eat at the very most one well Finn will eat four of them a day if given the chance. Granted theres poop all over but there do traces of the food anymore. It doesnt even get fat either its like those younger people hate so much they eat a truck load of chocalte and dont gain an ounce but you eat a single M&M and you gain 15pounds well my Pleco is the truck load eating one. I dont think theres enough food in the wild to keep this guy fool.

thats too many tablets......

i have 5 common plecos in a 125

biggets is 14 inches and smallest is 8 inches and i feed them algea tablets twice a week....6-8 each time

they have been in that tank for a month together and now they are getting split up as their tanks are back up and running

I dont think 8 is to much at all, plecos are big and need alot of food. You wouldnt feed your middle/top dwelling fish only a few times a week, so why do it with bottom feeders? I have bottom feeders, but not to scavenge, I have them because I like them. They get fed regularly just like the other fish.