Hello, Margie. A picture of the leaves would help determine clearly what you are seeing so see if any of my suggestions can help you identify the cause of the problem...

In the summer months, yellow leaves can be caused by watering issues (watering too much such that the roots cannot absorb much oxygen) so you need to get watering under control. You can use a soil moisture meter for this or you could just insert a finger into the soil to a depth of 4" to see if the soil feels dry or almost dry. If it does feel dry-ish then give the soil around the shrub 1.5 gallons of water (you can go down to 1 gallon in Spring, Fall and Winter). Also, try maintaining 3-4" of organic mulch to help with this issue as the mulch will minimize soil moisture evaporation somewhat.

But, yes, leaf yellowing in the summer can also be caused by too much sun. If the plant is getting too much sun, only the leaves in direct contact with the sun will turn yellow (the ones underneath and protected from the sun will remain green). This gives the shrub an odd look. If this is what you see then you may need to temporarily protect it thru the end of summer and then decide if you want to transplant it to a more shaded location. 30% shade cloth can be used. But feel free to construct anything that will provide shade (if this is the cause of the problem of course).

There are mineral deficiencies that can also cause yellowing of leaves. If the soil lacks nitrogen, the old leaves can start turning yellow. A cheap soil test kit that checks levels of NPK or a full-fledged soil test can help determine if you have this problem. The cheap soil test kits are available at plant nurseries. I feel that these gizmos are not quite exact but hey, all you care to know is if the minerals are too low or too high so in case like this, I do not worry about how precise they are and I just try to find out if N is low.

Near the end of the summer for me, there is the infamous iron chlorosis; but you really can have this issue at any time in the growing season. Iron chlorosis causes the leaves to yellow out but the leaf veins remain dark green. So if the leaves are all yellow, this is not your problem. Adding acidifying compounds corrects iron chlorosis. You can use aluminum sulfate, garden Sulphur, greensand, etc. You can also use liquid chelated iron compounds. The liquids deliver faster results but the others last longer. Either way, the leaves take a while to self correct. A soil pH kit can be used to regularly monitor this problem (say, every 2 months or so) and these kits can be purchased at most plant nurseries.

The red tinges may be the result of the leaves getting old or about to get a few leaf spots (a few is not a big issue). Water the soil and never the leaves. Then monitor the spots for changes and post again if you think there is a large problem with the leaves with red tinges.

Luis

Many people have simply gotten much more rain than average. If you *arent* manually watering, don't! It won't make the situation any better.

There are also many leaf/bloom blights that are associated with moisture, and with that, insect damage can also occur. Years with a higher percentage of drier days will alleviate many issues, but until such time we just have to try and live with it.

As for TnS coloration, the later into the season you get, the more reds you see (leaves, stems, blooms, you name it). By October the whole plant will appear to look like it's on FIRE!! But before then, sun also accelerates this. So, if you are experiencing a season where there is a LOW amount of sun (as many folks are this year), you'll see more green and for a longer period of time.

I'm not sure where you live, so I'm making assumptions. But the conditions I described are affecting more people than not.