Start testing the soil by inserting a finger into the soil to a depth of 2-3" so you can tell if the soil is dry, moist or wet. Then if it is wet, give them water; otherwise, if it is wet or moist, skip watering. You can also use a moisture meter to ck the moisture level.. Do these tests at about the same time daily for 2-3 weeks to get a feel for how often to water.

Light green colors might indicate that the plant soil needs more acidity so add more garden sulphur or aluminum sulphate.. Lots of water gets rid of these minerals so you have to add more regularly. Same thing would happen to the fertilizer minerals if you water often (meaning they would leech out).

Determine if the location is also windy as winds during the day can dry the leaves out. Temps around my area have gone close to the 90s and may require that I start watering extra too. Mine are in the ground and I give them 1g of water per watering but may have to water even more.

Make sure that they get shade by 11am or so. This may help blooms not go brown (but early browning is common on new hydrangeas as blooms dry out early or simply get old because the flower buds were forced to open early by the wholesaler. Newly planted hydrangeas suffer from transplant shock (leaves dry out, leaves wilt, blooms dry out, etc) but they get over it in 1-3 years. Florist hydrangeas, sold with names as "hydrangea" or "pink hydrangea" may be unusually sun/wind/heat sensitive in their first years to just about everything. By the way, where are you? I tend to let my new hydrangeas get used to the outside sun in bright shade before letting them get any direct morning sun. Helps with some of these leaf and bloom issues.

Thanks for the input1 I am worried about root rot. I will take a photo when I get home and post it.

Here are the photos. What do you think?

That will help. Root rot is actually difficult (but not impossible) to get if the potting soil that you have is well draining and there are exit holes for the water in the pot. I also try not to leave much water in the pans that I put under the potted plants. I assume you are watering once or twice a day? Do you know how much in gallons and how often?

The symptoms for root rot are similar to those of a plant that does not get water because the roots cannot channel much or any water up to the leaves. By the way, I am trying to get an idea of your USDA Zone and where you are located to see if the local weather also has something to do with the problems.

It looks like it is pushing new leaves, so I would remove the dried leaves and old blossoms and see how it does. As Luis said, check that the soil is moist, not soggy or dry, and be sure that the pot has drainage holes. You can feed it with time release fertilizer pellets since plants in pots need fertilizer since they are in potting mix rather than real soil.

That's for the input guys! I tested the soil and it is moist so I stopped watering. However, I don't have a way to test the acidity. I am trying to get the tools to do so. Luis, I am in Tampa Florida, zone 9b. I also have removed all the dead leaves and I'll attach photos of what it looks like. Why did they look so great when I bought them and now they are just sticks? The ones I have in the ground don't look like this but they are also not pushing any new leaves. Is this common in Florida?

Florida, oh well. Like NHBabs said, hydrangeas normally loose their leaves in the Fall and get new leaves in Spring but those grown in the "extreme" South can keep the leaves until they are about to leaf out or until a little after leaf out. I see that behavior in some of my oakleaf hydrangeas. The oakleaf hydrangeas comingle the old and new leaves but the mopheads -when we have mild winters- drop leaves first and afterwards open new leaves (or they may have a few, almost dead leaves at the same time as new leaves are just opening).

Maintain proper soil moisture: it should feel moist not wet; if you get a drop of water when pressing soil with two fingers then that is too much water (exceptions: it just rained; the sprinkler just watered the plants; you just watered the plants; etc), maintain proper amounts of soil minerals/amendments, mulch and see how they behave. Plants in the ground will also loose leaves but will not be in sync with potted plants.

Like luis_pr stated above, most hydrangeas loose all of there leaves in late fall and are semi dormant in winter. These growth cycles are often manipulated by nurseries so the plants are in full bloom by late winter/early spring, months before they would normally be. Your newly purchased plants may be simply resetting that cycle by dropping the old leaves which have already served a season and sending out new ones for a fresh start. The new leaves appear to be healthy from the photos and you may even get a few more blooms this season. Hope this helps. :)