thanks for all answers, i tried everything an here are the results:
1- i metered how many light was the old bulb and then replaced it for a new one, same EVs, so or all bulbs are bad or bulbs aren't the problem.
2- i did the coin test, perfect blacks and nice whites. So my chemicals and paper are ok.
3- i disassembled my enlarger, i noticed that grade filters were half way of the bulb light, so i force them to move up and now they seem to cover all light.
4- i shot an underexposed roll (two thirds of stop) and then overdeveloped at 50% more of my standard time,

I printed 3 photos to check the roll, and here it is, nice blacks, nice whites, nice tone separation, i guess that filters weren't a huge problem with all that dullness.

So can a diffuser enlarger need 50% more of development that a condenser one?
i didn't check any Zone density with that roll, but prior this one i tried to follow what AA said in his "The Negative" book about densities for a diffuser enlarger with no luck, do you know if there is any other densities table more indicated for me? or at least how can i make my own one to get new times, new isos....