Ro/Di water gaining tds is it ok to use

I have had a tub of water in the kitchen sealed for around 5 days. I tested the tds and it was around 57 so I thought I already put salt in it but then I tested it for salt and there was none in it. I have filtered another tub of RO water today and put salt in it and it was fine but by the time I had noticed the one with the high tds reading did not have any salt in it I had already taken out 2 tubs of water so now there is no water getting to my sump for serculation and filtration and I was wondering if this water would be ok? It the tds has gone up from the air it should be because the tank water gets sir to! But of it has came from the container it could be worse? They are plastic tube I got from the lfs and have only had salt water from the lfs in and now my own RO/Di water. Would you use this water? It's a 25 later tub for a 200 litre tank... I think that makes the tank ruffly 43 gallon tank and a 4 gallon tub of water