Can we put water back onto them and slow down this cure?
You misunderstand utterly. Concrete does not "dry" and cure - concrete sets and needs moisture to cure - it's a chemical reaction. Drying interferes with the curing process, being wet helps it proceed, and the concrete becomes stronger as it cures (by a very large factor.) So you are not trying to slow the cure, you are trying to keep it going, as you are slowing it by allowing the concrete to dry out.
The tank does not need to be full, but the walls need to be wet. You could put a sprayer, mister, or fogger in the tank for that purpose - you could put soaker hoses on the top of it and run them from a pump in the tank, or any number of ways to keep it wet. Covering with wet burlap is one method that helps to wick water up and prevent surface drying. Covering the wet fabric with plastic sheeting helps to keep it wet if water is not being continuously applied.
The following is quoted from Page 220 of this (book on the web, I guess, though it's just one chapter linked) Design and Control of Concrete Mixtures x EB001 http://www.ce.memphis.edu/1101/notes/concrete/PCA_manual/Chap12.pdf
It covers the fact that curing will resume, but you may not get the full strength of the concrete if delayed too long.
When moist curing is interrupted, the development of strength continues for a short period and then stops after the concrete’s internal relative humidity drops to about 80%. However, if moist curing is resumed, strength development will be reactivated, but the original potential strength may not be achieved. Although it can be done in a laboratory, it is difficult to resaturate concrete in the field. Thus, it is best to moist-cure the concrete continuously from the time it is placed and finished until it has gained sufficient strength, impermeability, and durability.
Loss of water will also cause the concrete to shrink, thus creating tensile stresses within the concrete. If these stresses develop before the concrete has attained adequate tensile strength, surface cracking can result. All exposed surfaces, including exposed edges and joints, must be protected against moisture evaporation.
Which is pretty much a direct answer to the title question: yes, it's better to manage the cure after mismanaging it than to compound the problem by continuing to mismanage it.
Page 221 notes:
If sprinkling is done at intervals, the concrete must be prevented from drying between applications of
water by using burlap or similar materials; otherwise alternate cycles of wetting and drying can cause surface crazing or cracking.
Page 221 clarifies:
Alternate cycles of wetting and drying during the early curing period may cause crazing of the surface.
