Bacteria are problem but if the shrimps are strong they should be OK.
Do you have individual tools for every single tank? If not, how you will stop infection to spread around?
Probably nobody wash his hands between feeding or maintain his/her/ next tank?
Probably only Donna has net, pipettes, tester, hose etc. in large numbers.
Heck, I wash my hands before I feed each individual tank and have separate tools for them. As far as stopping infection from spreading if you only have one set of tools, a good wipe down with vinegar and rinse after every use should get tackle most bacteria I would think. I wipe my tools down with vinegar and rinse before and after I use them. Doesn't matter if they are used for just one tank or not I just like my tools to be clean.