I had my pool/spa acid washed because there was some staining (I was already doing a complete drain and fill). The plaster is now a mess, it is very rough and traps dirt. I looks and feels terrible. I am thinking they left the acid on too long. I drained the spa and power washed and sanded the plaster. It is much better. There is still some light staining. Can I spray bleach on the stained areas (the spa is still empty) and then add water immediately. Will that make a difference on the stains (I have no idea what they are from)? Is there an easier approach than sanding and power washing? It is all I could think of. Thanks.