A word of caution while switching to full RO use, you will need to remineralize the RO anyway. Don't make the switch from tap to just RO as it will mess with hardness which seems already low and might explain why the neos aren't doing well. For neos, a gH of 6-7 is quite ok, lower and they start to have molting issues or shell issues. First, I would try to increase the gH in the tank to something close to 6 dgH. SaltyShrimp Bee Mineral raises just gH with minimal impact to TDS. Start doing water changes of about 5% every couple of days with tap water having a gH of 6. Afterwards, you can switch to RO remineralized to the same 6 degrees of hardness. You might want to consider buying a TDS meter if you don't have one already.