It would appear as though you are trying to re-fill 'old' cartridges. If you leave empty cartridges for any length of time, they get to the point that trying to refill them becomes unsatisfactory. Best to re-fill as soon as they show signs of becoming empty, this keeps the inner working moist.
Regarding the vent,you will find on an original or compatible cartridge the vent is usually taped over. Installing in the printer, then the tape is usually removed, otherwise the cartridge will not print.
You may also find that some re-fill procedures may cause an airlock, and this will lead to signs that the cartridge as dried up.On some cartridges you can insert a little air after you have put in the ink to the specified amounts. InkTec provide a venting device with their kits, or they use to do.
Any brand type refill ink, like JR or InkTec will do.
Was the cartridges that you filled, originals or compatibles, because this can make a slight difference.New originals will take more refills, because they were new to begin with. Compatibles may have only had one previous refill, and not knowing the manufacturers refill procedures can make a difference.Some refill companies, clean the old ink away before putting new ink as a replacement. Some manufacturers cut corners and can afford to perhaps sell cheaper.